In computer systems, additional functionalities may be added to such systems through the use of add-on hardware, such as plug-in modules or circuit boards. Such boards include, for example, wireless network cards, graphics processing cards, and television video decoder and tuner cards. Typically, when the computer system is operating, these cards draw power, even when they are not in use. For systems where the source of power is limited, such as laptop computers or mobile computing devices using a battery, power consumption due to idle plug-in hardware wastes valuable, limited energy resources.
In order to economize energy resources, it is known to physically unplug the plug-in cards to save power. Alternatively, it is also known to manually turn off plug-in cards or modules when not in use through a device manager, which is typically software, particularly in devices where such plug-in cards or modules are not easily accessible, such as in a laptop computer or mobile computing device, however, such device managers may not actually effect a total powering down of the card or module, thus still consuming power. Moreover, a manual on/off scheme relies upon a user to control power usage of the external hardware, which does not always provide accurate or current energy management. Additionally, in cases where an application may be requesting a currently powered down circuit module, a user must manually power up the plug-in module in order to enable the application to properly access the plug-in hardware.